The present invention relates generally to turbines and turbine blades and more particularly relates to tip shrouded turbine blades with center located cutter teeth.
A turbine assembly, such as that used in power generation, typically generates rotating shaft power by expanding hot compressed gas produced by combustion of a fuel. Gas turbine buckets or blades generally have an airfoil shape designed to convert the thermal and kinetic energy of the flow path gases into mechanical rotation of the rotor.
Turbine performance and efficiency may be enhanced by providing a seal at the tip of the bucket to block the flow of air over or around the top of the bucket that would otherwise bypass the bucket. For example, a tip shroud may be positioned on the end of the bucket opposite the end attached to the rotating shaft. The tip shroud generally includes a shelf and a sealing rail. This configuration reduces spillover by decreasing the size of the clearance gap and by interrupting the hot gas path around the end of the bucket. In addition, the sealing rail may have one or more cutter teeth thereon. The cutter teeth may further restrict spillover by cutting through a honeycomb-like structure that may surround the tip shroud.
Tip shrouds, however, are subject to creep damage due to the combination of high temperatures and centrifugally induce bending stresses. The failure of a single bucket or blade may cause the entire turbine to be taken offline. In addition to the downtime, such a repair of a bucket is time consuming and/or expensive.
There is a desire, therefore, for a turbine blade shroud with improved ability to handle temperature and stress. Such a turbine blade shroud should provide increased lifetime while also increasing the efficiency of the turbine system as whole.